Projector

ABSTRACT

A projector is provided which can realize a bright projected image of high light utilization efficiency while combining a reflective-type liquid crystal device and an integrator optical system. The projector may include a light source lamp, a light beam dividing optical element, a polarization conversion element, a polarization selection element having a polarization selection surface, and an electro-optical device. When a plane of incidence including a normal line of the polarization selection surface and the central axis of an incident light is assumed, the direction parallel to the plane of incidence and perpendicularly intersecting the central axis is assumed to be the X-axis direction, and the direction perpendicularly intersecting the plane of incidence is assumed to be the Y-axis direction, the direction of polarization beam separation by the polarization conversion element is the X-axis direction.

This is a Continuation of application Ser. No. 09/774,796 filed Feb. 1,2001 now abandoned. The entire disclosure of the prior application(s) ishereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a projector which divides light from alight source into a plurality of partial light beams, which converts theplurality of partial light beams into one type of polarized light beampolarized in substantially the same direction by a polarizationconversion element, which changes the polarized state of the polarizedlight beam by an electro-optical device, which selects a state by apolarization selection element to form an optical image according toimage information, and which enlarges and projects the optical image.

2. Description of Related Art

Recently, attention has been focused on projectors using areflective-type liquid crystal device. In such a reflective-type liquidcrystal device, the pixel density can be increased by forming astructure, such as a transistor, for driving liquid crystal under areflecting mirror. Therefore, the reflective-type liquid crystal devicehas the advantage of realizing a clear projected image with highresolution, compared with the case where a transmissive liquid crystaldevice is used.

In addition, in projectors using an electro-optical device, such as aliquid crystal device, in order to reduce the size of the entire devicewhile realizing a bright projected image without display nonuniformity,the use of an integrator optical system or a polarization conversionelement has been proposed (Japanese Unexamined Patent ApplicationPublication No. 8-34127, and Japanese Unexamined Patent ApplicationPublication No. 10-232430, etc.). In the integrator optical system,light from a light source is divided by a light beam dividing opticalelement into a plurality of partial light beams to form a plurality oflight source images, the light source images are considered as dummylight sources, and light from the plurality of light source images issuperposed on a liquid crystal panel, whereby illumination light havinga uniform intensity distribution can be obtained. In the polarizationconversion element, light from a light source is divided into aplurality of partial light beams to perform polarization conversion andthen, the light is superimposed on a liquid crystal device, wherebyillumination light polarized in the same direction is obtained.

For this reason, it is thought that a brighter projected image with highresolution and without display nonuniformity can be realized if theintegrator optical system and the polarization conversion element areused in combination in the projector using the reflective-type liquidcrystal device.

SUMMARY OF THE INVENTION

When a reflective-type liquid crystal device utilizing a polarizationmode as a display mode is used in a projector, a polarization selectionelement (for example, a polarization beam splitter) for spatiallyseparating and selecting light of different polarization states isgenerally used, but the polarization selecting characteristic of thepolarization selection element has strong incident-angle-dependency.More specifically, in the case where a plane of incidence including anearly central axis of the incident light and a normal line of apolarization selection surface of the polarization selection element isdefined, if the incident angle of light is increased in a planeperpendicularly intersecting the plane of incidence, the polarizationselectivity is substantially reduced. Since this phenomenon greatlydepends on a geometrical positional relationship between a polarizationselection surface and the light entering there, it is very difficult toprevent the substantial reduction in the polarization selectivity. Onthe other hand, if the incident angle of light is increased at the planeof incidence, the polarization selectivity is also reduced, but thedegree of reduction is relatively small as compared to that in the planeperpendicularly intersecting the plane of incidence, and the reductionin the polarization selectivity can be prevented by arranging theconfiguration of the polarization selection surface. Therefore, in orderto at least improve the polarization selectivity of the polarizationselection element, it is important to reduce the incident angle of lightin the plane perpendicularly intersecting the plane of incidence as muchas possible, for example.

In addition, the optical system employing the integrator optical systemor the polarization conversion element, by reason of its opticalprocess, cannot avoid the phenomenon in which the angular distributionof the incident angle of illumination light expands.

For this reason, in the case where the integrator optical system and thepolarization conversion element are used in combination in the projectorusing the reflective-type liquid crystal device, since the incidentangle of light entering the polarization selection surface is increased,the polarization selectivity of the polarization selection surface isreduced, causing a problem in that light utilization efficiency isreduced and non-uniform brightness occurs.

It is one object of the present invention to at least provide aprojector which can realize a bright projected image with high lightutilization efficiency and high quality while combining areflective-type liquid crystal device and an integrator optical systemor a polarization conversion element.

The projector according to the present invention achieves at least theabove object by, for example, arranging a direction of polarization beamseparation and characteristics of a light beam dividing optical element.

(1) The projector according to one exemplary embodiment of the presentinvention is a projector including a light beam dividing optical elementfor dividing light from a light source into a plurality of partial lightbeams; a polarization conversion element for converting the plurality ofpartial light beams into one type of polarized light beam polarizedsubstantially in the same directions; an electro-optical device formodulating an illumination light beam emitted from the polarizationconversion element; a projection lens for projecting light modulated bythe electro-optical device; and a polarization selection surface forselecting light of a predetermined polarized component included in theillumination light beam and emitting the light toward theelectro-optical device, and for selecting light of a predeterminedpolarized component in the light modulated by the electro-optical deviceand emitting the light toward the projection lens. In the projector,when a plane of incidence including a normal line of the polarizationselection surface and the central axis of the illumination light beam isassumed, the direction parallel to the plane of incidence andperpendicularly intersecting the central axis is defined as the X-axisdirection, and the direction perpendicularly intersecting the plane ofincidence is defined as the Y-axis direction, the direction ofpolarization beam separation by the polarization conversion element isthe X-axis direction.

According to the exemplary embodiment as described above, thepolarization beam separability of the polarization selection surface hasstrong incident-angle-dependency to an incident light beam. Inparticular, when an incident angle of light is increased in the Y-axisdirection perpendicularly intersecting the plane of incidence, thepolarization selectivity is remarkably reduced. On the other hand, inthe polarization conversion element, since two types of polarized lightbeams polarized in different directions are produced from the partiallight beams, the width of each partial light beam substantially doublesin the direction of separation, and the angular distribution of thelight expands. Thus, in order to improve the polarization selectivity inthe polarization selection element, it is important to consider theincident-angle-dependency of the polarization selectivity and the spreadof the angular distribution of the light incident thereon.

According to this exemplary embodiment, since the direction ofpolarization beam separation in the polarization conversion element isthe X-axis direction, an increase in the incident angle of light in theY-axis direction incident on the polarization selection surface can berestrained. Thus, the polarization selectivity can be maintained in arelatively high state, making it possible to realize a bright projectedimage having a high contrast ratio.

(2) As the electro-optical device, for example, a reflective-type liquidcrystal device disposed at a position on which either light transmittedor reflected by the polarization selection surface is incident,modulating the incident light, and emitting the modulated light from theplane of incidence of the light, may be adopted.

(3) The light beam dividing optical element may preferably be configuredso as to narrow the spacings of the plurality of light source images inthe Y-axis direction.

That is, since the increase in the incident angle of light in the Y-axisdirection can be further restrained by narrowing the spacings of thelight source images in the Y-axis direction, the polarizationselectivity of the polarization selection surface can be maintained in avery high state, making it possible to realize a very bright projectedimage having a high contrast ratio.

(3-1) As the light beam dividing optical element, a rod for reflectinglight incident from an incident end surface at plural pairs ofreflection surfaces, dividing the light according to differences inreflection positions, and emitting the light as a plurality of partiallight beams from an emission end surface, can be adopted.

As the rod, a solid one (solid rod) consisting of light-guidingmaterial, or a hollow one (hollow rod) having a light reflecting surfaceformed on the inside surface of a cylindrical member can be adopted. Inthe case of the solid rod, light is totally reflected by the reflectingsurface without optical loss, so that the light utilization efficiencycan be further increased. In the case of the hollow rod, since lightincident from the incident end surface reaches the emission end surfacevia an air layer in the rod, uniform illumination light can be realizedeven if the size between the incident end surface and the emission endsurface is set to be relatively short, and further, the hollow rod ismanufactured more easily than the solid rod.

When the solid rod or the hollow rod is adopted, it may include at leasttwo sets of reflecting surfaces opposing in the X-axis direction and inthe Y-axis direction, and the cross section of the rod can be formedinto a polygon of a tetragon or more, such as an octagon, a dodecagon,or the like.

However, if the light transmission efficiency from the light source tothe light beam dividing optical element is considered, since the lightincident on the light beam dividing optical element from the lightsource has a substantially circular cross section, the incident endsurface of the rod may preferably be formed in a square shape. Inaddition, if the illuminating efficiency to the subsequently disposedelectro-optical device is considered, since an image formed on theemission end surface of the rod is superimposed on a display area of theelectro-optical device that is one area to be illuminated, the emissionend surface of the rod may preferably have the shape substantiallysimilar to the shape of the display area of the electro-optical device.

In the case of adopting the above-described rod as the light beamdividing optical element, the spacings of the light source images in theY-axis direction can be narrowed by disposing the rod so that a spacingof a pair of the reflecting surfaces opposing in the Y-axis direction isgradually widened from the incident end surface toward the emission endsurface.

Furthermore, the rod may be disposed so that a spacing of a pair ofreflecting surfaces opposing in the X-axis direction is graduallynarrowed from the incident end surface toward the emission end surfaceof the rod. In this case, since the disposition spacings of the lightsource images in the X-axis direction can be widened, the spacingsbetween the polarization beam separation films and the reflecting filmsof the polarization conversion element can be set in sufficientconsideration of the sizes of the light source images. Thus, thepolarization conversion efficiency in the polarization conversionelement can be increased, and consequently, making it possible toincrease the light utilization efficiency in the projector.

(3-2) As the light beam dividing optical element, a lens array composedof a plurality of condenser lenses aligned in the X-axis direction andthe Y-axis direction can be also adopted.

In this case, it is possible to narrow the spacings of the plurality oflight source images in the Y-axis direction by designing the lightcollecting characteristics of the plurality of condenser lenses. As thecondenser lenses constituting the lens array, hologram lenses ordiffraction lenses for condensing light by a holographic effect ordiffraction can be also adopted in addition to a general lens.

In addition, since the images formed on the condenser lenses of the lensarray are superimposed on a display area of the electro-optical devicethat is one area to be illuminated, the condenser lenses may preferablyhave the shapes substantially similar to the shape of the display areaof the electro-optical device. This can increase the illuminationefficiency.

In addition, a part of or all of the plurality of the condenser lensesconstituting the lens array may preferably be a decentered lens.

That is, since the light source images can be formed at positions otherthan the physical centers of the condenser lenses by forming a part ofor all of the condenser lenses with the decentered lens, the spacings ofthe plurality of light source images formed on a virtual plane can befreely controlled.

(4) When the lens array is adopted as the light beam dividing opticalelement, a reducing optical system may preferably be disposed on anoptical path provided between the light source and the polarizationconversion element. By reducing the overall cross sectional size of theillumination light with the reducing optical system, the increase in theincident angle of light in the Y-axis direction can be furtherrestrained.

By the disposition of such a reducing optical system, the overall crosssectional size of the illumination light can be reduced in the Y-axisdirection. For this reason, the increase in the incident angle of lightin the Y-axis direction can be further restrained, and the polarizationselectivity of the polarization selection surface can be maintained in avery high state. Therefore, it is possible to realize a very brightprojected image having high contrast ratio. In addition, since theoverall diameter of the light beam illuminating the area to beilluminated can be reduced, an expensive lens having the small F-numberdoes not have to be adopted as the projection lens. Therefore, areduction in the cost of the projector can be realized.

In this case, not only the cross sectional size in the Y-axis direction,but also the cross sectional size in the X-axis direction may bereduced. In this case, it is possible to maintain the polarizationselectivity of the polarization selection surface in a higher state.

Such a reducing optical system can be constituted by at least one convexlens disposed on one of the incident side and the emission side of thelens array, and at least one concave lens disposed on the incident sideof the polarization selection element. In this case, in the case whereonly the cross sectional size in the Y-axis direction of theillumination light beam is reduced, cylindrical lenses can be used asthe concave lens and the convex lens. While the convex lens and theconcave lens can be constituted by one lens member, respectively, theymay preferably be a combined lens formed by a combination of a pluralityof lenses if the reduction in the optical aberration is considered.

(5) In the above projector, a reducing optical system for reducing thecross sectional size of the illumination light in the Y-direction can bedisposed between the polarization conversion element and thepolarization selection element.

While the reducing optical system can be constituted by one concavelens, it can be also constituted by a combined lens formed by acombination of a plurality of lenses. If the reduction in the opticalaberration is considered, the combined lens may preferably be adopted.In this case, cylindrical lenses can be used as the convex lens and theconcave lens.

By the adoption of such a reducing optical system, the same advantagesas in the case of (4) can be also obtained.

In addition, in this case, not only the cross sectional size of theillumination light in the Y-axis direction, but also the cross sectionalsize in the X-axis direction may be reduced. In this case, generalaxisymmetric curved lenses can be used as the concave lens and theconvex lens.

The convex lens and the concave lens constituting a series of the abovereducing optical systems may be hologram lenses or diffraction lensesfor condensing light by a holographic effect or diffraction, in additionto general lenses having surfaces formed into curved shapes.

(6) As the polarization conversion element, a polarization conversionelement including a polarization beam separation film for transmittingone polarized light beam and for reflecting the other polarized lightbeam in two types of polarized light beams, a reflecting film forreflecting the other polarized light beam, and a retardation film forunifying the directions of polarization of the two types of polarizedlight beams in order to unify the directions of emission of the twotypes of the polarized light beams, may preferably be adopted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing a first exemplary embodiment ofa projector of the present invention;

FIG. 2 is a schematic perspective view showing the relationship betweena rod and positions of light source images S in the embodiment;

FIGS. 3(a)-(b) include diagrams, each showing the configuration of apolarization conversion element in the embodiment, in which FIG. 3(a) isa horizontal sectional view, and FIG. 3(b) is an outward perspectiveview;

FIG. 4 is an illustration showing the geometric relationship between apolarization selection surface and a light beam incident thereon in theembodiment;

FIG. 5 is a schematic perspective view showing the relationship betweena rod and positions of light source images S according to a secondexemplary embodiment of the present invention;

FIG. 6 is a schematic perspective view showing the relationship betweena rod and positions of light source images S according to a thirdexemplary embodiment of the present invention;

FIG. 7 is a schematic horizontal sectional view showing a fourthexemplary embodiment of the projector of the present invention;

FIG. 8 is a schematic horizontal sectional view showing a fifthexemplary embodiment of the projector of the present invention;

FIGS. 9(a)-(b) show the schematic configuration of a sixth exemplaryembodiment of the projector of the present invention, in which FIG. 9(a)is a vertical sectional view as seen from the X-axis direction, and FIG.9(b) is a horizontal sectional view as seen from the Y-axis direction;

FIG. 10 is a vertical sectional view showing the schematic configurationof a seventh exemplary embodiment of the projector of the presentinvention;

FIGS. 11(a)-(b) include diagrams, each showing the schematicconfiguration of an eighth exemplary embodiment of the projector of thepresent invention, in which FIG. 11(a) is a vertical sectional view asseen from the X-axis direction, and FIG. 11(b) is a horizontal sectionalview as seen from the Y-axis direction;

FIG. 12 is a vertical sectional view showing the schematic configurationof a ninth exemplary embodiment of the projector of the presentinvention; and

FIG. 13 is a schematic horizontal sectional view showing a tenthexemplary embodiment of the projector of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The exemplary embodiments of the present invention will now be describedwith reference to the drawings. In the following description, the Z-axisdirection represents the direction of light propagation, the Y-axisdirection represents the direction of twelve o'clock (directionperpendicularly intersecting the plane of the figure in FIG. 1) from thedirection of light propagation, and the X-axis direction represents thedirection of three o'clock from the direction of light propagation. InFIG. 1 to FIG. 13, the same components are denoted by the same referencenumerals.

A. First Embodiment

FIG. 1 is a schematic plan view showing a first exemplary embodiment ofa projector of the present invention.

The projector includes an illuminating device 1, a polarization beamsplitter 60 which may include a polarization selection surface, a liquidcrystal device 1000 serving as an electro-optical device, and aprojection lens 300. The configuration of the projector is such thatlight emitted from the illuminating device 1 is modulated by the liquidcrystal device 1000 according to image information, and is enlarged andprojected by the projection lens 300 so as to form an projected image ona projection plane 2000.

1. Illuminating Device

The illuminating device 1 may include a light source lamp 10 disposedalong an imaginary illumination optical axis L, a rod 20 serving as alight beam dividing optical element for dividing light from the lightsource lamp 10 into a plurality of partial light beams forming aplurality of light source images, a relay optical system 30 fortransmitting an image on an emission end surface 26 of the rod 20 to anarea to be illuminated, and a polarization conversion element 40disposed in the relay optical system 30 to perform polarization beamseparation and polarization conversion. The area to be illuminated isformed by the liquid crystal device 1000 serving as an example of theelectro-optical device for producing an image by optical modulation. Theshape of a display plane of the liquid crystal device 1000 in thisembodiment is assumed to be the shape of square in which the size in theX-axis direction is equal to the size in the Y-axis direction.

1-1 Light Source Lamp

The light source lamp 10 may include a light source 11 for radiallyemitting light beams, and an elliptical reflector 12 for collecting thelight emitted from the light source 11. One of two focal points of theelliptical reflector 12 is set to be positioned at the light source 11or in the vicinity thereof, and the other focal point is set to bepositioned on an incident end surface 22 of the rod 20 or in thevicinity thereof. The light emitted from the light source 11 iscondensed near the incident end surface 22 of the rod 20 by theelliptical reflector 12, and enters the rod 20 in the condensed state. Aparabolic reflector or a spherical reflector may be used instead of theelliptical reflector 12. In this case, however, it is necessary toinstall a condenser element for condensing nearly parallel light emittedfrom the reflector toward the incident end surface 22 of the rod 20 onthe emission side of the reflector.

1-2 Light Beam Dividing Optical Element

The rod 20 serving as the light beam dividing optical element is amember for dividing the light from the light source lamp 10 into aplurality of partial light beams to form a plurality of light sourceimages S positioned in the X-Y plane approximately in a matrix.

The rod 20 is a bar-like solid rod formed by a transparent light-guidingmaterial, such as a glass material, and is a hexahedron. The rod 20includes the incident end surface 22 where the light enters, fourreflection surfaces 24 a, 24 b, 24 c, and 24 d for reflecting andtransmitting light, and the emission end surface 26 from which thetransmitted light is emitted, as shown in FIG. 2. In this case, sincetotal reflection without optical loss is effected and light istransmitted utilizing it on the four reflection surfaces 24 a, 24 b, 24c, and 24 d, the rod 20 can realize a high light-transmissionefficiency.

The cross sections of both the incident end surface 22 and the emissionend surface 26 on the X-Y plane have rectangular shapes. In particular,in the case of this embodiment, the incident end surface 22 and theemission end surface 26 are formed to have shapes substantially similarto the shape of the display area of the liquid crystal device 1000 thatis an area to be illuminated, that is, formed in the shape of square,respectively. The reflection surface 24 a and the reflection surface 24c are parallel to each other, and the reflection surface 24 b and thereflection surface 24 d are parallel to each other. The light incidenton the rod 20 is divided into a plurality of partial light beams havingdifferent emission angles from the emission end surface 26 according todifferences in reflection positions and the number of reflection at thereflection surfaces 24 a, 24 b, 24 c, and 24 d.

The plurality of partial light beams emitted from the rod 20 atdifferent angles are condensed by a condenser lens 31, and form theplurality of the light source images S approximately in a matrix in theX-Y plane which is nearly parallel to the emission end surface 26 andperpendicularly intersecting the illumination optical axis L at aposition separated from the rod 20 by a predetermined distance. The X-Yplane on which the plurality of light source images S are formed isreferred to as a virtual plane P.

On the virtual plane P on which the plurality of light source images Sare formed or in the vicinity thereof, a first transmission lens 50, apolarization conversion element 40, and a second transmission lens 52are disposed, as shown in FIG. 1.

1-3 Polarization Conversion Element

The polarization conversion element 40 has the function of convertingincident light into predetermined linear polarized light beams, FIG.3(a) is a horizontal sectional view for explaining the configurationthereof, and FIG. 3(b) is an outward perspective view.

The polarization conversion element 40 formed by including a pluralityof light-transmissive members 41A and 41B, a plurality of polarizationbeam separation films 42 and reflecting films 44 alternately disposedbetween the light-transmissive members, and retardation films 48 thatare polarization direction-rotating means provided at positionscorresponding to the polarization beam separation films 42. Thepolarization conversion element 40 is formed by alternately bonding thelight-transmissive member 41A having the polarization beam separationfilms 42 and the reflecting surfaces 44 formed thereon with thelight-transmissive member 41B having no polarization beam separationfilms 42 and the reflecting films 44 formed thereon by an adhesiveagent, and then by bonding the retardation films 48 to thelight-transmissive member 41B. This X-axis direction corresponds to theX-axis direction, and the Y-axis direction corresponds to the Y-axisdirection. All the polarization beam separation films 42 and thereflecting films 44 are not necessarily aligned in the same direction.For example, they can be placed so that the adjacent light-transmissivemembers 41A and 41B are folded and positioned using the Y-Z plane as aplane of symmetry. While all the spacings between the polarization beamseparation films 42 and the reflecting films 44 are equal in thisembodiment, they may be different.

For conveniences, in the surface of the polarization conversion element40 on the side of incidence of light, a surface directly correspondingto the polarization beam separation film 42 is referred to as a “surfaceof incidence 45A”, and a surface directly corresponding to thereflecting film 44 is referred to as a “surface of incidence 45B”.Similarly, in the surface on the side of emission of light, a surfacedirectly corresponding to the polarization beam separation film 42 isreferred to as an “emission surface 46A”, and a surface directlycorresponding to the reflecting film 44 is referred to as an “emissionsurface 46B”. Since the light-transmissive members 41A and 41B aredisposed as described above, a plurality of the surfaces of incidence45A and the surfaces of incidence 45B are alternately formed atpredetermined spacings along a direction of polarization beam separationin the polarization beam separation film 42, that is, along the X-axisdirection. Similarly, a plurality of the emission surfaces 46A and theemission surfaces 46B are alternately formed at predetermined spacingsalong the X-axis direction.

The polarization beam separation films 42 have the function of spatiallyseparating incident unpolarized light into two types of linear polarizedlight beams whose directions of polarization approximatelyperpendicularly intersect. That is, light incident on the polarizationbeam separation films 42 is separated into a first linear polarizedlight beam that is transmitted light transmitted by the polarizationbeam separation films 42, and a second linear polarized light beam thatis a reflected light reflected by the polarization beam separation films42 and a direction of propagation thereof is bent by approximately 90degrees. In this embodiment, the first linear polarized light beam isp-polarized light beam, and the second linear polarized light beam iss-polarized light beam, and the polarization beam separation films 42are formed to have characteristics and angles so that the s-polarizedlight beam, which is reflected light, is reflected nearly in parallelwith the X-axis direction. The polarization beam separation films 42 canbe realized by dielectric multilayer films.

The reflecting films 44 have the function of reflecting the reflectedlight from the polarization beam separation films 42 again and directingthe light toward the substantially same direction as the direction ofpropagation of the transmitted light. The reflecting film 44 can berealized by dielectric multilayer films or aluminum films.

The retardation films 48 have the function of bringing a direction ofpolarization of one of the polarized light beams of the transmittedlight and the reflected light into substantially coincidence with adirection of polarization of the other polarized light beam. In thisembodiment, λ/2 phase plates are used as the retardation films 48, andare selectively disposed only on the emission surfaces 46A, as shown inFIGS. 3(a) and 3(b). Therefore, only the direction of polarization oflight transmitted by the polarization beam separation films 42 isrotated by approximately 90 degrees, and most of light emitted from thepolarization conversion element 40 is converted into one type ofpolarized light beam. In this embodiment, most of light emitted from thepolarization conversion element 40 is converted into s-polarized lightbeam.

The type and the position of the retardation films are not limited aslong as they can unify directions of polarization of two polarized lightbeams separated by the polarization beam separation films 42 into onedirection of polarization of one type of polarized light beam. Forexample, a configuration may be such that retardation films havingdifferent optical characteristics are disposed on the emission surfaces46A and the emission surfaces 46B so as to unify the directions ofpolarization of polarized light beams passing through the retardationfilms.

Since the polarization conversion element 40 as described above is used,unpolarized light emitted from the light source lamp 10 can beefficiently converted into one type of polarized light beam. Therefore,in the liquid crystal device 1000 which can utilize only one type ofpolarized light beam, it is possible to increase light utilizationefficiency.

1-4 Relay Optical System

The relay optical system 30 is a transmission optical system fortransmitting an image formed on the emission end surface 26 of the rod20 to the liquid crystal device 1000 that is an area to be illuminated,as shown in FIG. 1. In this embodiment, the relay optical system 30 iscomposed of the condenser lens 31, the first transmission lens 50, thesecond transmission lens 52, and a collimator lens 32.

The condenser lens 31 is disposed in the vicinity of the emission endsurface 26 of the rod 20, and has the function of guiding partial lightbeams from the rod 20 into the polarization conversion element 40 viathe first transmission lens 50. While the condenser lens 31 of thisembodiment is composed of a combined lens of two condenser lenses 31 aand 31 b, it is not limited thereto, and a general single lens may beused. However, in order to reduce optical aberration that tends to occurwhen guiding the partial light beams to the polarization conversionelement 40, the combined lens or an aspherical lens is suitably used.

The first transmission lens 50 is a lens array in which a plurality ofrectangular condenser lenses 51 are combined approximately in a matrix,and has the function of efficiently guiding each of the plurality ofpartial light beams into the surface of incidence 45A (see FIGS.3(a)-(b)) of the polarization conversion element 40. The number and thedisposition of the condenser lenses 51 are determined so as tocorrespond to the number and the position of light source images Sformed by the partial light beams. While the shape of the condenserlenses 51 constituting the first transmission lens 50 is not restricted,a plurality of rectangular condenser lenses aligned two-dimensionallyand formed in the shape of a plate as in this embodiment are easilyutilized. In addition, if the first transmission lens 50 is configuredby using the plurality of condenser lenses 51, light-collectingcharacteristics of the condenser lenses 51 can be optimized, so thatoptical aberration that tends to occur when transmitting light beams canbe effectively reduced. However, the first transmission lens 50 may beconfigured by a single lens without using the plurality of condenserlenses according to the characteristic of the light beam emitted fromthe rod (for example, in the case of a small emission angle), andfurther, it is also possible to omit the first transmission lens.

The second transmission lens 52 is disposed on the emission side of thepolarization conversion element 40, and has the function of transmittinga plurality of partial light beams emitted from the polarizationconversion element 40 onto the liquid crystal device 1000 that is anarea to be illuminated, and superimposing the partial light beams on onearea to be illuminated. While the second transmission lens 52 of thisembodiment is constituted by one lens, it may be a lens array configuredby a plurality of lenses in a manner similar to the first transmissionlens 50.

In this embodiment, while the first transmission lens 50 is disposed onthe incident side of the polarization conversion element 40, and thesecond transmission lens 52 is disposed on the emission side of thepolarization conversion element 40, these transmission lenses 50 and 52may be disposed together on the incident side or the emission side ofthe polarization conversion element 40, and in this case, the functionsof the transmission lenses 50 and 52 may be put together to form onelens. In this case, the cost of the illuminating device can be reduced.In addition, in this embodiment, since the first transmission lens 50 isdisposed on the incident side of the polarization conversion element 40,the function of effectively guiding each of the plurality of partiallight beams into the surface of incidence 45A of the polarizationconversion element 40 is provided to the first transmission lens 50. Inaddition, since the second transmission lens 52 is disposed on theemission side of the polarization conversion element 40, the function ofsuperimposing the plurality of partial light beams on the liquid crystaldevice 1000 is provided to the second transmission lens 52. Thefunctions provided to the transmission lenses 50 and 52, however, may beappropriately changed according to the positions where the transmissionlenses 50 and 52 are disposed.

The collimator lens 32 is disposed on the incident side of the liquidcrystal device 1000 that is an area to be illuminated, and has thefunction of converting the plurality of partial light beams incident onthe liquid crystal device 1000 from the polarization conversion element40 via the second transmission lens 52 into light nearly parallel toeach of central axes thereof, and effectively guiding the light into theliquid crystal device 1000. Therefore, the collimator lens 32 is notnecessarily required, and it can be omitted.

Since the relay optical system 30 as described above is disposed, theimage formed on the emission end surface 26 of the rod 20 is enlarged orreduced, and is transmitted onto the liquid crystal device 1000 that isan area to be illuminated.

2. Polarization Beam Splitter, Liquid Crystal Device, Projection Lens

The polarization beam splitter 60 is formed by sandwiching and joiningthe polarization selection surface 62 between two rectangular prisms,and is an optical element having the function of separating anunpolarized light beam into two types of linear polarized light beamswhose directions of polarization nearly perpendicularly intersect. Thepolarization selection surface 62 is formed of a dielectric multilayerfilm in a manner similar to the polarization beam separation film 42forming the polarization conversion element 40.

S-polarized light beam emitted from the illuminating device 1 enters thepolarization beam splitter 60, is reflected by the polarizationselection surface 62, and is emitted toward the reflective-type liquidcrystal device 1000. The liquid crystal device 1000 modulates the lightaccording to external image signals (not shown) to change a polarizationstate. While the reflective-type liquid crystal device 1000 is wellknown, detailed description of the structure and the operation thereofwill be omitted.

Light modulated by the liquid crystal device 1000 enters thepolarization beam splitter 60. The light modulated by the liquid crystaldevice 1000 is partially converted into the p-polarized state accordingto the image signals, and a light beam converted into the p-polarizedstate is transmitted by the polarization selection surface 62, and isemitted toward the projection lens 300. The light emitted toward theprojection lens 300 is projected onto a projection plane 2000, such as ascreen, via the projection lens 300.

Two polarizers 70 and 72 disposed on the incident side and the emissionside of the polarization beam splitter 60 have the function of furtherincreasing the degree of polarization of polarized light beams passingthrough these polarizers. When the degree of the polarized light beamsemitted from the illuminating device 1 is sufficiently high, thepolarizer 70 can be omitted. Similarly, when the degree of polarizationof polarized light beams emitted from the polarization beam splitter 60toward the projection lens 300 is sufficiently high, the polarizer 72can be omitted.

In this embodiment, while the liquid crystal device 1000 is disposed ata position opposing the projection lens 300 across the polarization beamsplitter 60, the liquid crystal device 1000 can be also disposed at aposition opposing the illuminating device 1 across the polarization beamsplitter 60. In this case, the configuration may be such that thepolarization states of the illuminating light beams emitted from theilluminating device 1 may be unified in the p-polarized state in advanceso that the s-polarized light beam emitted from the liquid crystaldevice 1000 enters a projection optical system. Alternatively, thepolarization selection surface 62 of the polarization beam splitter 60may have characteristics of reflecting the p-polarized light beam andtransmitting the s-polarized light beam.

3. Relationship between Direction of Polarization Beam Separation andPolarization Selection Surface 62

FIG. 4 shows the geometric positional relationship between thepolarization selection surface 62 and a light beam incident thereon. InFIG. 4, a plane of incidence 4 is a virtual plane defined by a centralaxis 2 of an illuminating light beam incident on the polarizationselection surface 62 and the normal line H of the polarization selectionsurface 62, and is parallel to the X-Z plane.

The polarization beam separability of the polarization selection surface62 has strong incident-angle-dependency. That is, if the incident angleof light increases in the X-axis direction parallel to the plane ofincidence 4 or in the Y-axis direction perpendicularly intersecting theplane of incidence 4, the polarization beam separability is reduced. Aspreviously described, the polarization selection surface 62 reflects andemits the s-polarized light beam included in the illuminating lighttoward the liquid crystal device 1000, and selects and emits thep-polarized light beam in the light modulated by the liquid crystaldevice 1000 toward the projection lens 300. Therefore, when thepolarization beam separability of the polarization selection surface 62is reduced, the amount of s-polarized light beam guided to the liquidcrystal device 1000 is decreased, so that light utilization efficiencyis lowered and the projected image becomes dark. Moreover, since thefunction as a filter for selecting a specific polarized light beam inthe light modulated by the liquid crystal device 1000 is reduced, thecontrast ratio of the projected image is also lowered.

It is possible to sufficiently reduce the incident-angle-dependency inthe X-axis direction parallel to the plane of incidence 4 by arrangingthe structure (for example, a type of a dielectric film or a way ofconfiguration) of the polarization selection surface 62. On the otherhand, the incident-angle-dependency in the Y-axis directionperpendicularly intersecting the plane of incidence 4 cannot be resolvedby arranging the structure of the polarization selection surface 62because it is dominated by the geometric positional relationship betweenthe polarization selection surface 62 and the light incident thereon.Therefore, in order to maintain the polarization beam selectivity of thepolarization selection surface 62 when light is entered the polarizationselection surface 62 with an angle, it is particularly important todecrease the incident angle in the Y-axis direction perpendicularlyintersecting the plane of incidence 4.

Thus, in this embodiment, as shown in FIG. 1 and FIG. 3(a), thedirection of polarization beam separation by the polarization conversionelement 40 is the X-axis direction parallel to the plane of incidence 4to thereby prevent an increase in the incident angle in the Y-axisdirection. That is, since the polarization beam separation is effectedby the polarization conversion element 40 in the X-axis direction, theoverall diameter of the illuminating light beam is enlarged in theX-axis direction, but the overall diameter of the illuminating lightbeam in the Y-axis direction perpendicularly intersecting the plane ofincidence 4 is not enlarged. As a result, the increase in the incidentangle in the Y-axis direction perpendicularly intersecting the plane ofincidence 4 can be prevented, making it possible to maintain thepolarization beam separability in a relatively high state. Therefore, abright and high-contrast projected image can be realized.

B. Second Embodiment

The spacings of the light source images S formed on the virtual plane Pcan be arbitrarily controlled by adjusting the spacing of the reflectingsurfaces of the rod. If the spacing of the reflecting surfaces isgradually narrowed from the incident end surface to the emission endsurface, the spacings of the light source images S can be widened.Hereinafter, the state in which the spacing of the reflecting surfacesis gradually narrowed from the incident end surface toward the emissionend surface is referred to as a “tapered state”. Conversely, if thespacing of the reflecting surfaces is gradually widened from theincident end surface toward the emission end surface, the spacing of thelight source images can be narrowed. Hereinafter, the state in which thespacing of the reflecting surfaces is gradually widened from theincident end surface toward the emission end surface is referred to asan “inversely tapered state”.

This embodiment shows an exemplary embodiment in which the reflectingsurfaces of the rod opposing in the Y-axis direction are in theinversely tapered state, and is the same as the projector of the firstembodiment except the shape of the rod. Thus, description of portionsexcept the rod will be omitted. In addition, it is possible to applymodified forms of the components described in the first embodiment tothis embodiment.

FIG. 5 is a schematic perspective view showing the relationship betweena rod 210 and positions of light source images S. The cross sections ofboth an incident end surface 212 and an emission end surface 216 on theX-Y plane have rectangular shapes. In the case of this embodiment, theemission end surface 216 is formed to have a shape substantially similarto the shape of a liquid crystal device that is an area to beilluminated. A pair of reflecting surfaces 214 a and 214 c opposing inthe X-axis direction are parallel to each other. A pair of reflectingsurfaces 214 b and 214 d opposing in the Y-axis direction are in theinversely tapered state. For this reason, as compared with the case ofthe rod 20 in the first embodiment, the placement spacings of theplurality of light source images S are narrowed in the Y-axis directionin which the pair of reflecting surfaces 214 b and 214 d in theinversely tapered state oppose.

Therefore, in this embodiment, the increase in the incident angle in theY-axis direction perpendicularly intersecting the plane of incidence 4of the polarization selection surface 62 can be further restrained,making it possible to maintain the polarization beam separability of thepolarization selection surface 62 in a considerably high state.

Furthermore, in this embodiment, as a result of narrowing the placementspacings of the light source images S in the Y-axis direction, the sizein the Y-axis direction of the polarization conversion element 40 andthe polarization beam splitter can be reduced, whereby the size and costof the illuminating device can be reduced and the size and cost of theprojector can be reduced. Furthermore, the size of the projection lens300 can be reduced, and a bright projected image can be realized even ifa small-aperture lens is used.

C. Third Embodiment

A third exemplary embodiment of the present invention will now bedescribed. This embodiment shows an embodiment in which reflectingsurfaces of a rod opposing in the Y-axis direction are in the inverselytapered state in a manner similar to the second embodiment, and further,reflecting surfaces of the rod opposing in the X-axis direction are inthe tapered state, and is the same as the projector of the firstembodiment except the shape of the rod. Thus, description of portionsexcept the rod will be omitted. In addition, it is also possible toapply modified forms of the components described in the first embodimentto this embodiment.

FIG. 6 is a schematic perspective view showing the relationship betweena rod 220 and positions of light source images S. The cross section ofan emission end surface 226 of the rod 220 on the X-Y plane has arectangular shape. In the case of this embodiment, the incident endsurface 222 and the emission end surface 226 are formed to have a shapesubstantially similar to the shape of a liquid crystal device that is anarea to be illuminated. A pair of reflecting surfaces 224 b and 224 dopposing in the Y-axis direction are in the inversely tapered state. Forthis reason, as compared with the case of the rod 20 in the firstembodiment, the placement spacings of a plurality of light source imagesS are narrowed in the Y-axis direction in which the pair of reflectingsurfaces 224 b and 224 d in the inversely tapered state oppose.Therefore, according to this embodiment, the same advantages as thesecond embodiment can be obtained.

Furthermore, in this embodiment, a pair of reflecting surfaces 224 a and224 c opposing in the X-axis direction are in the tapered state. Forthis reason, as compared with the case of the rod 20 in the firstembodiment, the placement spacings of the plurality of light sourceimages S are widened in the X-axis direction in which the pair ofreflecting surfaces 224 a and 224 c in the tapered state oppose.

The relationship between the polarization conversion efficiency of thepolarization conversion element 40 and the position of incidence oflight will be described with reference to FIGS. 3(a) and 3(b). Asdescribed in the first embodiment, the polarization conversion element40 separates light illuminated on the surface of incidence 45A andincident on the polarization beam separation films 42 into p-polarizedlight beam and s-polarized light beam, reflects the s-polarized lightbeam by the reflecting films 44 in the same direction as the p-polarizedlight beam, converts the p-polarized light beam into s-polarized lightbeam by the retardation films 48, and finally emits the s-polarizedlight beam. If light is illuminated on the surface of incidence 45B ofthe polarization conversion element 40, however, the light enters thepolarization beam separation films 42 via the reflecting films 44.Therefore, the first polarized light beam is transmitted by thepolarization beam separation films 42 in the X-axis direction, and thesecond polarized light beam is reflected by the polarization beamseparation films 42 in the Z-axis direction. As a result, polarizedlight beam different from that directly incident on the polarizationbeam separation films 42 via the surface of incidence 45A is emittedfrom the emission surfaces 46A and 46B. That is, although unpolarizedlight beam is to be converted into the second polarized light beam, thefirst polarized light beam is emitted by the polarization conversionelement 40, whereby the polarization conversion efficiency is lowered.This reveals that, in order to obtain high polarization conversionefficiency of the polarization conversion element 40, it is veryimportant to selectively allow a light beam to only enter the surface ofincidence 45A. That is, it is preferable that the spacings between thepolarization beam separation films 42 and the reflecting films 44 areset so that the size of the surface of incidence 45B is larger than thesizes of the light source images S.

In this embodiment, the spacings of the light source images S in theX-axis direction are widened so that the size of the surface ofincidence 45A can be sufficiently larger than the sizes of the lightsource images S. Therefore, the light beam from the rod 220 can enteronly the portion of the surface of incidence 45A of the polarizationbeam separation films 42 with a sufficient allowance, and the incidentefficiency of light on the polarization beam separation film 42 can besecurely increased. As a result, it becomes possible to increase lightutilization efficiency in the projector while securely increasing thepolarization conversion efficiency of the polarization conversionelement 40.

When the light source lamp 10 is close to a point light source, thesizes of the light source images S can be made relatively small.Therefore, in this case, it is not necessary to widen the placementspacings of the light source images S in the X-axis direction. That is,this embodiment is very effective for a case where the light source 11is not very close to the point light source, and the sizes of the lightsource images S increase.

D. Fourth Embodiment

FIG. 7 is a horizontal sectional view showing the schematicconfiguration of a fourth exemplary embodiment of the present invention.The fourth embodiment partially differs from the first embodiment in theconfiguration of the illuminating device. Other configurations are thesame as the previously described first embodiment. Thus, description ofthe same configurations as the first embodiment will be omitted. Inaddition, it is also possible to apply modified forms of the componentsdescribed in the first embodiment to this embodiment. In FIG. 7, thepolarization beam splitter 60, the polarizers 70 and 72, the projectionlens 300, and the projection plane 2000 are omitted.

An illuminating device 1A may include a light source lamp 15, a lensarray 600, a first transmission lens 610, a polarization conversionelement 40, a second transmission lens 620, and a collimator lens 32.This embodiment is characterized in that the lens array 600 consistingof a plurality of condenser lenses is used as a light beam dividingoptical element instead of the rod. The illuminating device 1A divideslight emitted from the light source lamp 15 into a plurality of partiallight beams by the lens array 600, converts the partial light beams intoone type of polarized light beam by the polarization conversion element40, and then superimposes the polarized light beam on a display area ofa liquid crystal device 1000 that is an area to be illuminated.

The light source lamp 15 may include a light source 11 for emittinglight, and a parabolic reflector 14 for collecting light emitted fromthe light source 11. The reflector is not limited to the parabolicreflector, and it is possible to use an elliptical reflector or aspherical reflector according to the configurations of the lens array600, the transmission lenses 610 and 620, the polarization conversionelement 40, and the like disposed on the downstream of light source lamp15.

The lens array 600 has a plurality of condenser lenses 600 a arrangedsubstantially in a matrix. The external shape of each of the condenserlens 600 a is set so as to be similar to the shape of the display areaof the liquid crystal device 1000 that is the area to be illuminated.Light incident on the lens array 600 from the light source lamp 15 isdivided into a plurality of partial light beams by the light collectingaction of each condenser lens 600 a to form as many light source imagesas the number of the condenser lenses 600 a in the X-Y plane, which issubstantially perpendicular to the illumination optical axis L,substantially in a matrix. The condenser lenses 600 a are set to havelight collecting characteristics such that a plurality of light sourceimages are formed only on the surface of incidence 45A (see FIGS.3(a)-(b)) of the polarization conversion element 40. In this embodiment,by partially adopting a decentered lens in a part of the plurality ofcondenser lenses 600 a, the spacings of the light source images to beformed are controlled.

Furthermore, the first transmission lens 610 disposed on the incidentside of the polarization conversion element 40 has approximately thesame function as the first transmission lens 50 in the first embodiment.The first transmission lens 610 has as many condenser lenses 610 a asthe number of the condenser lenses 600 a constituting the lens array600. In this embodiment, a part of the condenser lenses 610 a isconstituted by a decentered lens. The configuration is such that thecondenser lenses 610 a are positioned so as to correspond to positionswhere a plurality of light source images are formed. The lightcollecting characteristic of the condenser lenses 610 is set so that thepartial light beams divided by the lens array 600 enter nearlyperpendicularly the surface of incidence 45A of the polarizationconversion element 40 (see FIGS. 3(a)-(b)). Therefore, since light canenter the surface of incidence 45A of the polarization conversionelement 40 at an incident angle near 0 degree, it is possible toincrease the polarization conversion efficiency. While the shape of eachcondenser lens 610 a is not restricted, a rectangular or hexagonal shapeis convenient because it is easily arrayed.

The second transmission lens 620 has the same function as the secondtransmission lens 52 in the first embodiment, that is, the function ofsuperimposing the partial light beams divided by the lens array 600 onthe display area of the liquid crystal device 1000 that is an area to beilluminated. While the second transmission lens 620 is formed of oneaxisymmetric spherical lens in this embodiment, it is not limitedthereto. For example, a lens array, a Fresnel lens, a combined lensconsisting of a plurality of lenses or the like, can be also adopted.When such a lens is used, various types of optical aberrations can bereduced. The use of the Fresnel lens is favorable for reducing theweight of the illuminating device 1A because the central thickness ofthe lens can be reduced.

In this embodiment, it is also possible to obtain the same advantages asthe first embodiment.

While the decentered lens is partially used in the condenser lenses 600a and 610 a constituting the lens array 600 and the first transmissionlens 610 in this embodiment, the decentered lens does not have to beused. In addition, all of the condenser lenses 600 a and 610 a may bethe decentered lenses. In this embodiment, it is possible to set thelight collecting characteristics of the condenser lenses 600 a of thelens array 600 such that the placement spacings of the light sourceimages in the Y-axis direction are narrowed. Furthermore, it is alsopossible to set the light collecting characteristics such that theplacement spacings in the X-axis direction are widened. By setting thelight collecting characteristics of the condenser lenses 600 a in thisway, it is possible to obtain the same advantages as the secondembodiment and the third embodiment.

E. Fifth Embodiment

FIG. 8 is a horizontal sectional view showing the schematicconfiguration of a fifth exemplary embodiment. The fifth embodiment is amodification of the above-described fourth embodiment, and differs fromthe fourth embodiment in that a first transmission lens 612 is disposedbetween the polarization conversion element 40 and the secondtransmission lens 620. Other points are the same as the fourthembodiment. Thus, description of the same configuration as the fourthembodiment will be omitted. In addition, it also possible to applymodified forms of the components described in the fourth embodiment tothis embodiment. In FIG. 8, the polarization beam splitter 60, thepolarizers 70 and 72, the projection lens 300, and the projection plane2000 are omitted.

The first transmission lens 612 is, as is the first transmission lens610 in the fourth embodiment, a lens array composed of a plurality ofcondenser lenses 612 a. While the first transmission lens 610 in thefourth embodiment has the function of allowing the partial light beamsto nearly perpendicularly enter the surface of incidence 45A of thepolarization conversion element 40, the first transmission lens 612 ofthis embodiment does not have such a function because it is disposed onthe emission side of the polarization conversion element 40. Theconfiguration of this embodiment practically omits the firsttransmission lens 610 of the fourth embodiment. Therefore, theconfiguration is easily adopted when characteristics of light emittedfrom the light source lamp 15, for example, parallelism is excellent.

The basic action and effect of this embodiment are the same as theaction and effect of the fourth embodiment. According to thisembodiment, however, since the number of interfaces can be decreased byoptically combining the first transmission lens 612 and the secondtransmission lens 620, optical loss can be decreased. In addition, sincethe first transmission lens 612 is also provided with the function ofthe second transmission lens 620, it is possible to omit the secondtransmission lens 620, and to reduce the cost of the illuminating deviceand the projector.

While one condenser lens 612 a corresponds to the emission surface 46Aand the emission surface 46B (see FIGS. 3(a)-(b)) of the polarizationconversion element 40 in this embodiment, if the condenser lenses 612 aare disposed so as to provide one-to-one correspondence to the emissionsurface 46A and the emission surface 46B of the polarization conversionelement 40, that is, if the first transmission lens 612 is formed usingdouble the number of the condenser lenses 612 a in FIG. 8, it ispossible to further increase the light utilization efficiency of thefirst transmission lens 612.

F. Sixth Embodiment

FIGS. 9(a)-(b) show the schematic configuration of a sixth exemplaryembodiment of the projector of the present invention in which FIG. 9(a)is a vertical sectional view as seen from the X-axis direction, and FIG.9(b) is a horizontal sectional view as seen from the Y-axis direction.

The sixth embodiment is a modification of the previously describedfourth embodiment, and is characterized in that an afocal optical system700 serving as a reducing optical system is disposed between the lensarray 600 and the first transmission lens 610. Other points are the sameas the fourth embodiment. Thus, description of the same configuration asthe fourth embodiment will be omitted. It is also possible to applymodified forms of the components described in the fourth embodiment tothis embodiment. In FIGS. 9(a) and 9(b), the polarization beam splitter60, the polarizers 70 and 72, the projection lens 300, and theprojection plane 2000 are omitted.

The afocal optical system 700 has the function of reducing a diameter ofoverall light beams without much deteriorating parallelism of lightpassing therethrough. In this embodiment, the afocal optical system 700is constituted by a cylindrical convex lens 710 and a cylindricalconcave lens 712 each having a curvature only in the Y-axis direction.The function equivalent to that of the cylindrical lenses 710 and 712can be also realized by a combined lens consisting of two or morelenses. In this case, the optical aberration can be reduced. Thecylindrical convex lens 710 is set on the emission side of the lensarray 600, and refracts light passing through the cylindrical convexlens 710 only in the Y-axis direction to turn the light toward theillumination optical axis L. On the other hand, the cylindrical concavelens 712 is set on the incident side of the first transmission lens 610,and substantially collimates the turned light from the cylindricalconvex lens 710 with respect to the illumination optical axis L. In thisembodiment, since the afocal optical system 700 constituted by thecylindrical lenses 710 and 712 each having the curvature only in theY-axis direction is used in this way, the spread of a light beam in theY-axis direction can be further restrained, making it possible tomaintain the polarization beam separability of the polarizationselection surface in a considerably high state. Therefore, it ispossible to realize a very bright and high-contrast projected image.Furthermore, in this embodiment, as a result of restraint of the lightbeam in the Y-axis direction, the sizes of the polarization conversionelement 40 and the polarization beam splitter 60 in the Y-axis directioncan be reduced, whereby a reduction in size and cost of the illuminatingdevice, and a reduction in size and cost of the projector can beachieved.

In addition, the size of the projection lens 300 can be also reduced,and a bright projected image can be realized even if a small-aperturelens is used.

Furthermore, in the case of this embodiment, it is possible to easilymaintain the polarization beam separability in a high state withoutsetting the light collecting characteristics of condenser lenses 600 aof the lens array 600 in the Y-axis direction in a complicated manner.

While the cylindrical lenses 710 and 712 each having the curvature onlyin the Y-axis direction are used in this embodiment, a lens having thecurvature in two directions, or a toric lens may be used. This makes itpossible to restrain the spread of the overall light beams in the X-axisdirection, and the polarization beam separability of the polarizationselection surface 62 can be maintained in a higher state.

G. Illuminating Device according to Seventh Embodiment

FIG. 10 is a vertical sectional view showing the schematic configurationof a seventh exemplary embodiment of the projector of the presentinvention. The seventh embodiment is a modification of theabove-described sixth embodiment, and is characterized in that acylindrical convex lens 710 constituting an afocal optical system 700serving as a reducing optical system is placed on the incident side of alens array 600 serving as a light beam dividing optical element. Sinceother configurations are the same as the sixth embodiment, descriptionthereof will be omitted. In addition, it is possible to apply modifiedforms of the components described in the sixth embodiment to thisembodiment. In FIG. 10, the polarization beam splitter 60, thepolarizers 70 and 72, the projection lens 300, and the projection plane2000 are omitted.

Even if the position of the cylindrical convex lens 710 is changed as inthis embodiment, it is possible to achieve the same action and effect asthe sixth embodiment.

A configuration may be such that a cylindrical concave lens 712 isdisposed on the emission side of a first transmission lens 610.

H. Eighth Embodiment

FIGS. 11(a)-(b) include diagrams each showing the schematicconfiguration of an eighth exemplary embodiment of the projector of thepresent invention, in which FIG. 11(a) is a vertical sectional view asseen from the X-axis direction, and FIG. 11(b) is a horizontal verticalview as seen from the Y-axis direction. The eighth embodiment is amodification of the previously described sixth and seventh embodiments,and is characterized in that the function of the afocal optical systemis provided to the lens array 600 and the first transmission lens 610 inthe sixth and seventh embodiments. That is, a lens array 800 serving asa light beam dividing optical element and a first transmission lens 810realize the afocal optical system serving as a reducing optical system.In addition, it is possible to apply modified forms of the componentsdescribed in the sixth and seventh embodiment to this embodiment. InFIGS. 11(a) and 11(b), the polarization beam splitter 60, the polarizers70 and 72, the projection lens 300, and the projection plane 2000 areomitted.

The lens array 800 is constituted by a plurality of condenser lenses 800a arranged in a matrix. Light emitted from a light source lamp 15 isdivided into a plurality of partial light beams by the light collectingaction of the condenser lenses 800 a to form as many light source imagesas the number of the condenser lenses 800 a in the X-Y plane nearlyperpendicularly intersecting an illumination optical axis L. Inaddition, the lens array 800, as is the cylindrical convex lens 710 inthe sixth and seventh embodiments, has the function of refracting lightin the Y-axis direction to turn the light toward the illuminationoptical axis L.

The first transmission lens 810 is constituted by a plurality ofcondenser lenses 810 a arranged in a matrix. The configuration is suchthat the positions of the condenser lenses 810 a correspond to positionswhere a plurality of light source images are formed. The lightcollecting characteristics of the condenser lenses 810 a are set so thatthe partial light beams passing through the condenser lenses 810 anearly perpendicularly enter the surface of incidence 45A of thepolarization conversion element 40. In addition, the fist transmissionlens 810, as is the cylindrical concave lens 712 in the sixth andseventh embodiments, has the function of substantially collimating lightwith respect to the illumination optical axis L.

By this embodiment, it is also possible to achieve the same action andeffect as the above-described sixth and seventh embodiments.Furthermore, since the same function as the afocal optical system 700 ofthe sixth and seventh embodiments can be realized by the lens array 800serving as the light beam dividing optical element and the firsttransmission lens 810, it is possible to realize reductions in size,weight, and cost of the illuminating device by reducing the number ofmembers.

I. Illuminating Device according to Ninth Embodiment

FIG. 12 is a vertical sectional view showing the schematic configurationof a ninth exemplary embodiment of the projector of the presentinvention.

The ninth embodiment is a modification of the previously describedfourth embodiment, and is characterized in that a concave lens system900 serving as a reducing optical system is placed between a secondtransmission lens 620 and a collimator lens 32. Other points are thesame as the fourth embodiment. Thus, description of the sameconfigurations as the fourth embodiment will be omitted. In addition, itis also possible to apply modified forms of the components described inthe fourth embodiment to this embodiment. In FIG. 12, a polarizationbeam splitter 60, the polarizers 70 and 72, the projection lens 300, andthe projection plane 2000 are omitted.

The concave lens system 900 is composed of a combined lens formed by acombination of two concave lenses 900 a and 900 b in order to reduce theoptical aberration, and has an action of compressing a diameter of theoverall light beams in the X-direction and the Y-axis direction.Therefore, the spread of the light beam in the Y-axis direction and theX-axis direction can be further restrained, making it possible tomaintain the polarization beam separability in a considerably highstate. Thus, a very bright and high-contrast projected image can berealized. Furthermore, in this embodiment, as a result of restraint ofthe light beam in the Y-axis direction and the X-axis direction, thesizes of the polarization conversion element 40 and the polarizationbeam splitter 60 can be reduced, and a reduction in size and cost of theilluminating device, and a reduction in size and cost of the projectorcan be achieved. In addition, the size of the projection lens 300 can bereduced, and a bright projected image can be realized even if asmall-aperture lens is used.

A configuration may be such that the concave lens system 900 is acylindrical concave lens having the curvature only in the Y-axisdirection to restrain the spread of light in the Y-axis direction. Inaddition, the concave lens system 900 may be used in the projector usingthe rod as in the first to third embodiments.

J. Tenth Embodiment

FIG. 13 is a schematic horizontal sectional view showing a principalpart of the projector according to a tenth exemplary embodiment of thepresent invention. This embodiment is a modification of the projectoraccording to the above first to ninth embodiments, and is characterizedin that light emitted from a polarization beam splitter 60 is separatedinto red light, blue light and green light using a wedge-shaped prismserving as a spectral device, and colored lights enter into threereflective-type liquid crystal devices provided in correspondence withthe colored light to realize a color image. The configuration part shownin FIG. 13 is a part that can be replaced by the configurationssubsequent to the collimator lens 32 of the first to ninth embodiments.Both illustration and description of a portion toward the light sourcefrom the collimator lens 32, the projection lens 300, and the projectionplane 2000 will be omitted.

The color separating device 100 is formed by a combination of threeprisms 100 a, 100 b, and 100c. The wedge-shaped prism 100 a is formed inthe columnar shape having a triangular cross section, and a dichroicfilm R for reflecting the red light and transmitting other coloredlights is formed on a surface thereof adjacent to the wedge-shaped prism100 b. The wedge-shaped prism 100 a is disposed between the polarizationbeam splitter 60 and the wedge-shaped prism 100 b so as to have verysmall clearances. The wedge-shaped prism 100 b has the shape similar tothe wedge-shaped prism 100 a, and a dichroic film B for reflecting bluelight and transmitting other colored lights is formed on the surfacethereof bonded to the wedge-shaped prism 100 c. The prism 100 c is acolumnar prism having a substantially trapezoidal cross section in whicheach one side is formed as an oblique line. A plane equivalent to theoblique line of the prism 100 c is bonded to the plane of the wedge-likeprism 100 b on which the dichroic film B for blue light is formed.

A liquid crystal device 1000R is a reflective-type liquid crystal devicespecially designed for the red light, and is set to face a plane onwhich the dichroic film R for the red light of the wedge-shaped prism100 a is not formed, and which is not adjacent to the polarization beamsplitter 60. In addition, a liquid crystal device 1000B is areflective-type liquid crystal device specially designed for the bluelight, and is set to face a plane on which the dichroic film B for theblue light of the wedge-shaped prism 100 b is not formed and which isnot adjacent to the wedge-shaped prism 100 a. Furthermore, a liquidcrystal device 1000G is a reflective-type liquid crystal devicespecially designed for the green light, and is set to face a planeequivalent to an opposite side of the oblique line of the prism 100 c.The basic structures of the liquid crystal devices 1000R, 1000B, and1000G are the same as the liquid crystal device 1000 used in the aboveembodiments, and optical characteristics of liquid crystal layers andpixel electrodes are optimized according to the wavelength region of thecorresponding colored light.

In this embodiment, a polarized light beam (for example, s-polarizedlight beam) emitted from the illuminating device and reflected by apolarization selection surface 62 of the polarization beam splitter 60firstly enter the wedge-shaped prism 100 a to be -separated into a redlight to be reflected by the dichroic film R for the red light, and ablue light and a green light to be transmitted by the dichroic film Rfor the red light. The red light reflected by the dichroic film R forthe red light is totally reflected at an interface of the wedge-shapedprism 100 a facing the polarization beam splitter 60 and then, entersthe liquid crystal device 1000R for the red light, and is modulatedbased on external image information (not shown). Next, the blue lightand the green light transmitted by the dichroic film R for the red lightenter the wedge-shaped prism 100 b to be separated into a blue lightreflected by the dichroic film B for the blue light and a green lighttransmitted by the dichroic film G for the blue light. The blue lightreflected by the dichroic film B for the blue light is totally reflectedat an interface of the wedge-shaped prism 100 b facing the wedge-shapedprism 100 a and then, enters the liquid crystal device 1000B speciallydesigned for the blue light, and is modulated based on external imageinformation (not shown). Finally, the green light transmitted by thedichroic film B for the blue light goes substantially straight in theprism 100 c to enter the liquid crystal device 1000G specially designedfor the green light, and is modulated based on external imageinformation (not shown).

Each of the colored lights reflected by each of the liquid crystaldevices 1000R, 1000B, and 1000G, returns through the same optical pathat the time of entering to be synthesized as a projected light, andenters the polarized beam splitter 60 again. Since the polarized lightbeams modulated by the external image information are partiallyp-polarized light beams, the polarized light beams are transmitted bythe polarization selection surface 62, and are enlarged and projected ona front projection plane 2000 by a projection lens 300 serving as aprojection means. Three colored lights modulated by the three liquidcrystal devices 1000R, 1000G, and 1000B are projected onto theprojection plane 2000 by the above process so as to be superimposed atthe same position, and display a color image. A configuration may beadopted in which the color separating device 100 is disposed at aposition to oppose the illuminating device across the polarization beamsplitter 60. In this case, the polarization state of illumination lightemitted from the illuminating device is unified in the p-polarized stateso that s-polarized light beams emitted from the reflective-type liquidcrystal devices 1000R, 1000R, 1000G, and 1000B enter the projection lens300.

In this embodiment, the sizes of the polarization beam splitter 60 andthe like are relatively large, compared with the sizes of the liquidcrystal devices 1000R, 1000G, and 1000B, as shown in FIG. 13. For thisreason, in particular, the combination of this embodiment with the fifthto eighth embodiments in which the afocal optical system 700 serving asa reducing optical system and the concave lens system 900 are adopted isconvenient for realizing a reduction in size of the polarization beamsplitter 60.

According to this embodiment, it is possible to obtain the sameadvantage as one of the first to ninth embodiments.

K. Other Embodiments

The embodiments of the present invention is not limited to theabove-described examples, and various modifications can be made withinthe scope of the invention. For example, while the rods 20, 210, and 220are composed of solid rods consisting of light-guiding materials in theabove first to third embodiments, the rod may be cylindrical hollow rodformed by a member having a light-reflecting surface, for example, areflecting mirror (surface-reflecting mirror is desirable). In thiscase, light is reflected by a reflection surface directed to the insideof the hollow rod, and the light propagates in air having a lowrefractive index as compared with a glass material or the like. Asurface of a common reflecting mirror or the reflecting mirror on whicha reflection-enhancing film is formed by a dielectric body can be usedfor the reflection surface. Since the hollow rod can be manufacturedeasier than the solid rod consisting of a mass of the light-guidingmaterials, it is possible to reduce the cost of the illuminating deviceto be lower than the case where the solid rod is used. Furthermore,since air having a refractive index almost equal to 1 is contained inthe hollow rod, the sizes of the rods 20, 210, and 220 in the Z-axisdirection can be made shorter than the case where the solid rod having arefractive index larger than 1, and there is a possibility of reducingthe size of the illuminating device, and the size of the projector.

In addition, the projector may be either of a rear-type in which ascreen is projected from rearward, or a front-type in which the screenis projected from the front.

What is claimed is:
 1. A projector, comprising: a light beam dividingoptical element that divides light from a light source into a pluralityof partial light beams; a polarization conversion element that convertsthe plurality of partial light beams into one type of polarized lightbeam polarized substantially in same directions; an electro-opticaldevice that modulates an illumination light beam emitted from thepolarization conversion element; a projection lens that projects lightmodulated by the electro-optical device; and a polarization selectionsurface that selects light of a predetermined polarized componentincluded in the illumination light beam, the polarization selectionsurface reflects the light toward the electro-optical device, selectslight of a predetermined polarized component in the light modulated bythe electro-optical device and emits the light toward the projectionlens, wherein the direction of polarization beam separation by thepolarization conversion element is in an X-axis direction, when a planedefined by a normal line of a polarization selection surface and acentral axis of the illumination light beam is assumed to be a plane ofincidence, a direction parallel to the plane of incidence andperpendicularly intersecting the central axis is defined as the X-axisdirection, and a direction perpendicularly intersecting the plane ofincidence is defined as the Y-axis direction, the electro-optical devicebeing a reflective-type liquid crystal device disposed at a position onwhich either light transmitted or reflected by the polarizationselection surface is incident, modulating the incident light, andemitting the modulated light from the plane of incidence of the light,the light beam dividing optical element being configured so as to narrowspacings of a plurality of light source images in the Y-axis direction.2. The projector as claimed in claim 1, the light beam dividing opticalelement being a rod that reflects light incident from an incident endsurface at a plurality of pairs of reflection surfaces, that divides thelight according to differences in reflection positions, and that emitsthe light as a plurality of partial light beams from an emission endsurface, and the rod being disposed so that a spacing of a pair of thereflection surfaces opposing in the Y-axis direction is graduallywidened from the incident end surface toward the emission end surface.3. The projector as claimed in claim 2, the rod being disposed so that aspacing of a pair of the reflection surfaces facing in the X-axisdirection is gradually narrowed from the incident end surface toward theemission end surface.
 4. The projector as claimed in claim 2, theemission end surface of the rod having a shape substantially similar toa shape of a display area of the electro-optical device.
 5. Theprojector as claimed in claim 2, the rod being composed of a solidlight-guiding member consisting of a light-guiding material.
 6. Theprojector as claimed in claim 2, the rod being composed of a hollowlight-guiding member having a light-reflecting surface formed on aninside surface of a cylindrical member.
 7. The projector as claimed inclaim 1, the light beam dividing optical element being a lens arraycomposed of a plurality of condenser lenses aligned in the X-axisdirection and the Y-axis direction.
 8. The projector as claimed in claim7, the plurality of condenser lenses having shapes substantially similarto a shape of a display area of the electro-optical device.
 9. Theprojector as claimed in claim 7, the plurality of condenser lensesincluding a decentered lens.
 10. The projector as claimed in claim 7,further comprising a reducing optical system that reduces an overallcross sectional size of the illumination light beam in the Y-axisdirection disposed between the light source and the polarizationconversion element.
 11. The projector as claimed in claim 10, thereducing optical system further reducing the overall cross sectionalsize of the illumination light beam also in the X-axis direction. 12.The projector as claimed in claim 10, the reducing optical systemcomprising at least one convex lens disposed on one of the incident sideand the emission side of the light beam dividing optical element, and atleast one concave lens disposed on the incident side of the polarizationconversion element.
 13. The projector as claimed in claim 12, at leastone of the convex lens and the concave lens being formed by acombination of two or more lenses.
 14. The projector as claimed in claim1, the polarization conversion element including a polarization beamseparation film that transmits one polarized light beam and thatreflects another polarized light beam in two types of polarized lightbeams, a reflecting film that reflects the other polarized light beam,and a retardation film that unifies the directions of polarization ofthe two types of polarized light beams in order to unify directions ofemission of the two types of the polarized light beams.
 15. A projector,comprising: a light beam dividing optical element that divides lightfrom a light source into a plurality of partial light beams; apolarization conversion element that converts the plurality of partiallight beams into one type of polarized light beam polarizedsubstantially in same directions; an electro-optical device thatmodulates an illumination light beam emitted from the polarizationconversion element; a projection lens that projects light modulated bythe electro-optical device; a polarization selection surface thatselects light of a predetermined polarized component included in theillumination light beam, the polarization selection surface reflects thelight toward the electro-optical device, selects light of apredetermined polarized component in the light modulated by theelectro-optical device and emits the light toward the projection lens;and a reducing optical system that reduces an overall cross sectionalsize of the illumination light beam in the Y-axis direction disposedbetween the polarization conversion element and the polarizationselection surface, wherein the direction of polarization beam separationby the polarization conversion element is in an X-axis direction, when aplane defined by a normal line of a polarization selection surface and acentral axis of the illumination light beam is assumed to be a plane ofincidence, a direction parallel to the plane of incidence andperpendicularly intersecting the central axis is defined as the X-axisdirection, and a direction perpendicularly intersecting the plane ofincidence is defined as the Y-axis direction.
 16. The projector asclaimed in claim 15, the reducing optical system further reducing theoverall cross sectional size of the light beam consisting of a pluralityof partial light beams in the X-axis direction.
 17. The projector asclaimed in claim 15, the reducing optical system being a combined lensformed by using at least one or more concave lenses.
 18. The projectoras claimed in claim 15, the reducing optical system being composed of acylindrical lens.